1. Field of the Invention
The present invention relates to a fuel injector in particular used in an internal combustion engine, that enables the metered injection of the fuel to be combusted.
2. Description of the Prior Art
DE 103 25 620 A1 has disclosed a servo valve-controlled fuel injector with a pressure booster. The fuel injector disclosed therein includes a pressure booster, whose booster piston divides a working chamber, which is acted on with fuel by means of a pressure accumulator, from a differential pressure chamber, which can be pressure-relieved. A pressure change in the differential pressure chamber occurs through an actuation of the servo valve, which opens or closes a hydraulic connection of the differential pressure chamber to a first low-pressure side return. The servo valve also has a servo valve piston guided between a control chamber and a first hydraulic chamber. This servo valve piston has a hydraulic surface, which continuously acts on the servo valve piston in the opening direction when it is acted on by system pressure, and a first sealing seat that closes or opens a low-pressure side return. Activation of the pressure booster, however, requires a switching valve that activates a servo valve piston, which requires a significant structural complexity. In addition, aforementioned piezoelectric actuators can be used in order to circumvent the requirement for a switching valve.
DE 10 2004 015 744 A1 has disclosed a fuel injector of this generic type for the injection of fuel into a combustion chamber of an internal combustion engine, having an injector housing that has a fuel inlet, which is connected to a central high-pressure fuel source outside of the injector housing and is connected to a pressure chamber inside the injector housing, from which highly pressurized fuel is injected as a function of the position of the control valve, in particular a 3/2-way directional control valve. In this case, the 3/2-way directional control valve is provided with a valve piston, which is hydraulically coupled to the piezoelectric actuator and can be acted on with the pressure from the high-pressure fuel source. The valve piston in this case is situated in a valve control chamber and produces a seal against sealing edges that are situated in the sealing control chamber itself.
In the known embodiments of fuel injectors of interest here, the problem arises that the 3/2-way directional control valve and in particular, the axially movable valve piston contained therein, must be embodied in a complex fashion, which results in a significant production cost. For the correspondingly precise embodiment of the valve piston, complex matching grinding processes of the sealing seat are required, it being necessary for these sealing seats to be produced concentrically to each other in the valve body itself.